Weather strips are typically formed of an olefin-based polymer (rubber, thermoplastic resin, or thermoplastic elastomer). In particular, for weather strips, such as a glass run which is attached to a window frame portion so that glass makes sliding contact therewith, an inner weather strip, and an outer weather strip, the following means to improve the glass sliding properties are known.
(1) Addition of Silicone Compound
Patent Document 1 describes a sliding material obtained by extruding a raw material in which 5% by weight to 20% by weight of a silicone compound is blended with an olefin-based polymer, and a weather strip in which the surface portion of the weather strip making sliding contact with glass is molded using the sliding material.
However, although providing sliding properties, a silicone compound also causes the problem that, when the silicone compound is blended in a large amount, the adhesive properties to a molded portion are reduced, and accordingly, a process of cutting out the section is needed.
(2) Mixing of Resin Particles
Patent Document 2 describes a method of producing a weather strip, in which an olefin-based thermoplastic elastomer is used as a material for a weather strip body; a synthetic resin obtained by mixing polyethylene powder or particles with a base material made of an olefin-based resin is used as a material for a thin protective film; and the olefin thermoplastic elastomer and the synthetic resin are co-extrusion-molded using two extruders. Patent Document 2 describes that, since the polyethylene powder or particles to be used have high viscosity and low fluidity, the powder or particles are extrusion-molded with the form thereof being maintained to some extent, and a rough surface portion with fine asperities is formed in the surface of the weather strip.
However, the study of the present inventors indicated the problem that, since a resin was used for the base material for a thin protective film, this caused inferior flexibility.
Patent Document 3 describes a composition produced by blending acrylic modified organopolysiloxane with an olefin-based thermoplastic elastomer formed of a polymer crosslinked by dynamically dispersing and kneading an ethylene-based copolymer rubber in an olefin-based resin, and furthermore by blending at least one particulate powder (having an average particle diameter of 30 μm to 80 μm) selected from polyethylene-based particulate powder, polystyrene-based particulate powder, and acrylic particulate powder with the resulting mixture. In addition, Patent Document 3 describes molding a portion, making sliding contact with glass, of a weather strip by using the composition.
However, the study of the present inventors revealed that sufficient sliding properties were not achieved even using this method.